National Luna Intelligent Solenoid
National Luna Intelligent Solenoid
Compatibility: Read Before Ordering
This solenoid works seamlessly with the National Luna Dual Battery Controller. It is NOT compatible with the National Luna Dual Battery Monitor. These are two different products and pairing the solenoid with the Monitor will not work. If you already own a monitor or controller and are not sure which one it is, call us at 844-200-3979 before ordering and we will sort it out with you.
The National Luna Intelligent Solenoid is the brains behind a dual battery setup. It is a compact, automatic, parallel split-charge isolator that manages charging and isolation between your starter battery and your auxiliary battery with no input from you. Run your fridge, lights, and accessories off the aux battery all night, and the solenoid guarantees your starter battery still has the charge to turn the engine over in the morning.
The install is refreshingly simple for a dual battery component. It piggy-backs directly off your vehicle's main battery with no ignition tapping and no modification to factory wiring. Nothing gets cut or spliced into your vehicle's harness. Under the hood, it uses intelligent control electronics paired with a low-loss, high-current solenoid rated for extreme environments and 85 amps continuous. Available in two versions: the standard Original, and a Land Rover spec model with a grey base to match Land Rover engine bay hardware.
How It Works
The whole system runs on voltage sensing. No ignition wire, no manual switch, no thinking about it. Here is the full cycle:
You start the vehicle
The solenoid senses incoming voltage greater than 13.1V, which tells it the alternator is running and putting out charge.
Five minute timer runs
It holds the batteries isolated for 5 minutes, sending the full alternator output to your primary battery so it can recover from the current draw of cranking the engine. Your starter battery gets priority.
Circuit closes, aux battery charges
After the timer expires, the solenoid closes the circuit automatically and current flows to your secondary battery. Both batteries now charge in parallel off the alternator.
You shut the vehicle off
System voltage drops below 12.7V. The solenoid opens the circuit and isolates the two batteries from each other. Your fridge and accessories now draw only from the aux battery.
Starter battery stays protected
The batteries stay isolated until the solenoid sees more than 13.1V again. No matter how flat you run the aux battery overnight, the starter battery is untouched and the truck starts in the morning. Then the cycle repeats.
This process is fully automated. You never manually manage the charging of the second battery, and there is nothing to remember to switch on or off at camp.
Add a Dual Battery Controller
We strongly recommend pairing the Intelligent Solenoid with the National Luna Dual Battery Controller (sold separately). It mounts to your dashboard and shows the live charge and storage status of both batteries, so you know exactly where your aux battery sits before you commit to another night out. It also includes an override function that lets you manually combine the batteries if you ever need the aux battery to help restart the vehicle. That override alone has saved plenty of trips.
See It in Action
Specifications
| Product Type | Automatic parallel split-charge isolator (dual battery) |
| Continuous Current | 85 Amps |
| Charge Engage Threshold | Greater than 13.1V |
| Isolate Threshold | Less than 12.7V |
| Priority Charge Delay | 5 minute internal timer |
| Ignition Sense | Not required |
| Factory Wiring Modification | None. Piggy-backs off the main battery |
| Solenoid | Durable, low-loss, rated for extreme environments |
| Control | Intelligent control electronics, fully automatic |
| Compatible Accessory | National Luna Dual Battery Controller (sold separately) |
| NOT Compatible With | National Luna Dual Battery Monitor |
| Original Stock Code | BMS-20001 |
| Land Rover Spec Stock Code | BMS-20005 (grey base) |
What's Included
Not included: Cables, lugs, batteries, battery monitor, or other hardware. These are available separately. Plan your cable gauge and fusing based on your run length and current draw, or call us and we will help you spec it.
📄 Installation Instructions
Download the full Intelligent Solenoid installation manual before you start wiring.
Pros
- Fully automatic. No switches to flip, nothing to remember at camp
- 85A continuous capability handles fridges, lights, inverters, and accessory loads
- No ignition tapping and no cutting into factory wiring. Piggy-backs off the main battery
- 5 minute priority delay lets your starter battery recover from cranking before the aux battery draws charge
- Voltage-sensing design means it works on any 12V vehicle without model-specific wiring
- Low-loss solenoid rated for extreme environments and engine bay heat
- Land Rover spec version available with a grey base to match factory hardware
Cons
- Supplied as the solenoid only. Cables, lugs, batteries, and monitoring hardware are all sold separately, so budget for a complete install
- Not compatible with the National Luna Dual Battery Monitor. You need the Dual Battery Controller if you want dash-mounted status and override
- Wiring a dual battery system requires correct cable gauge and fusing. If you are not confident with 12V electrical work, budget for professional installation
Frequently Asked Questions
Will this drain my starter battery if I run a fridge overnight?
No. That is exactly what it prevents. When you shut the vehicle off and system voltage drops below 12.7V, the solenoid opens the circuit and physically isolates the two batteries. Your fridge and accessories draw only from the aux battery. No matter how flat you run the aux side overnight, the starter battery is electrically separate and untouched, so the truck starts in the morning.
Do I have to cut into my vehicle's wiring?
No. The Intelligent Solenoid piggy-backs off your vehicle's main battery and requires no ignition sense wire. Because it triggers purely on voltage rather than an ignition signal, there is no tapping into your factory harness and no splicing. This keeps your vehicle wiring intact, which matters for warranty, resale, and troubleshooting down the road.
Why the 5 minute delay before the aux battery charges?
Starting an engine pulls a large amount of current out of your primary battery. The 5 minute timer holds the batteries isolated so the full alternator output goes into recovering the starter battery first. Only once that window passes does the solenoid close the circuit and start charging the aux battery. It is a small detail that meaningfully extends the life of your starter battery over years of use.
What do I need to buy alongside it?
The solenoid ships on its own as a fully functional isolator. You will also need an auxiliary battery, appropriately sized cable and lugs for your run length, and fusing. We strongly recommend adding the National Luna Dual Battery Controller for dash-mounted status readout and the manual override function. Call us at 844-200-3979 and we can walk through your build and spec the whole system with you.
What is the difference between the Original and Land Rover versions?
Functionally they are identical. Both are 85A intelligent split-charge isolators with the same voltage thresholds and the same automatic operation. The Land Rover spec unit (BMS-20005) has a grey base rather than the standard finish, sized and finished to suit Land Rover engine bay mounting. Choose whichever suits your vehicle using the variant selector above.
Complete Your Power System
Questions About Your Dual Battery Setup?
We will confirm controller compatibility, help spec your cable and fusing, and plan the whole system.
844-200-3979
